In considering the morality of the actual willful installation of madness into the mind of another because that person's desire for the madness, one must decide whether the lack of madness is something to be desired and is valuable to the individual, whether the willful incursion of madness itself is moral, and finally if there is anything that would make the actual act of removing that which would leave a mind mad an act which prevents the losing party to complete duties or is contrary to the duty of the actor which is removing the said qualities.
My answer, simply, would be a yes, it is moral. In normalcy or typicalness there is all that we all experience and specific to this person's normalcy there is what he himself experiences. We know from the post that this is a source of great pain and depression so we can see the continuation of normal perceptions and actions is detrimental. In madness there is a quality that you would seek, especially in the questions motivation and inherency, that would diminish pain and suffering, and therefore be something that would provide comfort and prevent future lasting comfort as madness often leaves one with a profound impermanence of mental states. As such, the first condition for morality is met.
The second is also met in that madness is a state of mind in which the mind is altered from a normal (here meaning average and typical for comparable machines) mind into one which has varied perception as mentioned above. This is also the effect of drugs, especially hallucinogens, which inherently have no moral good or bad to them, simply the state of being mind altering. This neutrality, though, is not enough to say it is permissible morally. To do so, two things could be done: Universality tests or analysis of the state to see if it is a beneficial end. The first passes clearly, as the universality test outlined by Kant in his Grounding for the Metaphysics of Morals just asks if I could say that everyone should or should be allowed to do this very same thing. I say yes, that the removal of a complete or typical consciousness as we know it is acceptable for anyone to take should that be what they want to do. The analysis of benefits, something a bit more Mills-ian, would simply do a small impact calculus to see whether the incurred madness is better or worse for the world. In his case, he is relieved from suffering and the world loses one of 6+ billion individuals slaving away at who knows what... not doing it means he suffers and the world still has him doing shit. He is insignificant in the macro and the alleviation has already been shown to be astronomical in the micro and as such, he is good to go.
The third consideration, the one of duties, is a bit tougher. The first idea is that one must do what is right and secondly do it for the right reasons. What is right though? Well it would be said that the right thing to do is that which is in accord with the universal moral laws of the universe, which are said to be those laws which would be in accord with the will and cognition of the proper mind. The proper mind is that mind which would produce the best actions should all minds take those actions and in the net results of time, the best existence for all that live as sentient or rational beings. Lets consider what that means in totality. The first bit about the universal moral law of the universe implies that it is the same for all beings in all places and all times regardless of context. That is an objective stance which requires that all wills and cognitions in all proper minds are universally in accord with each other. It is also true that those two qualities then must be logical equivalents to the quality of a mind which seeks the greatest ends for all existence. Part of all minds, rational and mad, is the quality of preservation insofar as preservation is the best thing for the mind, and the mad mind is capable of ending that preservation should it not be the best, whereas the rational one is often too occupied with objects outside itself to recognize when the time has come for it to end or is too attached to let itself go completely. I think that this is the event that has occurred with this persons mind, so it s slowly seeking out the control or lack thereof to complete the dutiful task. Therefore, it is in promotion of the mind's duty for the one who would receive madness.
The final question is if it is in conflict with the duties of the actor which would induce the madness. I would be inclined to say no. An actor who would induce madness willingly upon a subject who wishes the madness (and therefore would be benefited by it) would ultimately be benefiting the soon to be maddened. In addition to benefiting others, considerations of other duties exist and are self preservation when proper and to tell truth. These are the principles that constitute the foundations for all morals and insofar as the methods for causing madness are not physically or emotionally destructive (deconstructiveness of the conscious mind is not inherently harmful as the rational mind is evidently capable of constructing pain and damage to itself and other faculties of the human experience) and that it doesn't require use of lies, both of which are a matter of specific procedurals and irrelevant to whether or not the act of brining on madness itself insofar as they are not inherent to the act.
Hopefully that little bit helped you see if that is or isn't moral.